[R-sig-Geo] Proj4string for NASA GPW v3 and Blue Marble world city light map?

[Ziyu Ma]

Dear all,

I was working with a project concerning human population, using data from
the Population Density Grid, version 3.

I have hard time understanding the spatial reference from this metadata
page:

http://sedac.ciesin.columbia.edu/data/set/gpw-v3-population-density/metadata

Can I translate this into a proj4string so that I can use it as a CRS in R?

Also, just out of curiosity, what it the spatial reference for NASA's Blue
Marble maps, like the famous world city light map? Can I also use a
proj4string to describe it?

Thank you very much.

Cheers,
Ma

Ziyu Ma
PhD Student
Ecoinformatics & Biodiversity,
Department of Bioscience, Aarhus University
Ny Munkegade 114, DK-8000 Aarhus C, Denmark

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